This invention is directed to a method for achieving and maintaining an inert atmosphere which is as oxygen-deficient as possible within a treatment chamber. More particularly, this invention is directed to a method wherein an irradiation chamber is traversed by a length of material which is supplied to the chamber through an inlet channel and is conducted from the chamber through an outlet channel and wherein the maximum oxygen concentration in the reaction space is prevented from exceeding 200 ppm and more preferably from exceeding 100 ppm.
This invention is directed also to an apparatus for implementing the aforementioned method.
Supporting sheets coated with cured synthetic resin are used to a considerable extent, for example, as adhesive or release papers. For their preparation, the supporting sheets are generally coated with a radiation-curable polymer, such as an acrylic resin, and subjected to the action of suitable radiation, in order to effect the curing of the polymer. This curing reaction takes place in a very short time, so that lengths of material coated with curable resin can be passed by a suitable source of radiation for the purpose of curing at high speed. Since the free radical polymerization or curing is impeded or prevented by oxygen, it is necessary that the supporting sheets treated with curable resin be supplied to a treatment chamber which has an inert gas atmosphere. However, during the transport of the resin-coated supporting sheet, air is brought into the treatment chamber. Care must be taken, therefore, to ensure that the maximum oxygen concentration of .ltoreq.200 ppm of oxygen in the treatment chamber is not exceeded by this entrained air.